The preparation of unsaturated carboxylic esters such as methyl methacrylate or methyl acrylate from isobutylene or propylene is known in the art. U.S. Pat. No. 3,325,534 discloses such a method wherein the unsaturated nitrile is reacted with water and an oxyacid such as sulfuric acid to form a unsaturated carboxylic acid. This acid is then esterified with an alcohol. A major disadvantage with these processes however, is that they require a plurality of reactors, one reactor to convert the olefin to an aldehyde, one to convert the aldehyde to acid, and one to convert the acid to its corresponding ester.
Direct oxidation of propylene or isobutylene to an aldehyde is well known in the art. See U.S. Pat. Nos. 3,264,225 and 3,387,038. The latter two reactants, conversion of an aldehyde to an acid and an acid to an ester have been combined into one step. See for example, U.S. Pat. No. 3,819,685 showing the preparation of esters from unsaturated aldehydes and alcohols.
The present invention carries the formation of esters one step further by combining all three reactions in a single fluid bed reactor, thereby greatly reducing the cost and complexity of producing these esters.